(a) Technical Field
The present disclosure relates generally to a method for manufacturing a separator integrated with a gasket of a fuel cell stack. More particularly, the present disclosure relates to a method for manufacturing a separator of a fuel cell stack, which prevents a separator from being contaminated when a gasket is formed and cross-linked on the separator of a fuel cell stack.
(b) Background Art
In general, a fuel cell using polymer electrolytes generates electricity and heat via the electrochemical reaction of fuel gas containing hydrogen with oxidizer gas containing oxygen. The core component of the polymer electrolyte fuel cell, in which a reaction occurs, is a Membrane Electrode Assembly (MEA) which includes a polymer electrolyte membrane, a pair of electrodes formed on both surfaces of the polymer electrolyte membrane, and a gas diffusion layer. The polymer electrolyte fuel cell requires a separator which enables the flow of reactant gas to the MEA. The separator has a passage and a manifold hole formed therein in order to control the flow of reactant gas and cooling medium. A fuel cell stack is manufactured by stacking the MEA and the separator in a desired quantity.
Meanwhile, a gasket can be formed around the electrode (or the passage) and the manifold hole in the separator in order to prevent a reactant gas and a cooling medium from mixing with each other. In order to form the gasket, conventional methods use a gasket which is formed and processed in advance, form a gasket on a separator using a liquid gasket material, etc.
In the method of applying the liquid gasket material onto the separator to form the gasket, a metal separator is manufactured by coating the surface of the separator and then integrating the coated separator with a gasket. For example, the method of manufacturing the metal separator may include a process of manufacturing a molded separator, a process of coating the surface of the separator, a process of injection molding a gasket on the separator, a process of cross-linking the gasket, etc.—which may be executed in this order. In the method of manufacturing the metal separator integrated with the gasket, the contact resistance of the separator may be increased in the gasket forming process.
According to the result of exposure simulation with respect to process variables of gasket processing environments (e.g., air, high temperature, foreign substances, etc.), it has been identified that the change in contact resistance of the separator is insignificant in the high temperature/air, but that the surface contamination of the separator due to foreign substances causes an increase in contact resistance. In the case where the gasket forming process is performed after the surface coating (i.e., surface treatment) of the separator, when contaminants are present on the coated surface of the separator, it is difficult to secure the movement path of electrons since the effective area for electric conduction is relatively reduced, thereby causing an increase in contact resistance of the separator due to foreign substances.
Since the increase in contact resistance of the separator directly causes deterioration of performance of the fuel cell stack, it is necessary to reduce and minimize the contact resistance of the separator. In addition, contact resistance is one of the indicators of quality in the mass production of metal separators. Accordingly, when the contact resistance of a metal separator is higher than a predetermined level, the metal separator is determined to be faulty.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.